This invention relates to a scanning exposure apparatus provided with a plurality of optical projecting systems and a plurality of illumination systems, and also to an exposure method. In particular, this invention relates to a scanning exposure apparatus wherein the adjustment of position among the optical systems thereof can be facilitated to thereby make it suited for performing the exposure of substrate which has been deformed in the processing of the substrate, and also to an exposure method which is suited for performing the exposure of substrate which has been deformed in the processing of the substrate.
In recent years, due to the reasons that a prominent improvement in display quality has been made in the liquid crystal diaplay apparatus and that the liquid crystal display apparatus is thin in structure and light in weight, the liquid crystal display apparatus is now increasingly employed as an image display device in place of the CRT. In particular, there has been a prominent advance in enlarging the active area of direct viewing type liquid crystal panel of active matrix system, so that the size of glass substrate to be employed for manufacturing such an enlarged liquid crystal panel is also increasingly enlarged.
As for the exposure apparatus for carrying out an exposure for forming an element pattern of display panel on such a large glass substrate, there is known a scanning exposure apparatus wherein an original image pattern image formed on a photomask or reticle (hereinafter referred to simply as a mask) is projected through an optical projecting system on the surface of the glass substrate (hereinafter referred to also as a photosensitive substrate), and concurrently, the mask and photosensitive substrate are scanned relative to the optical projecting system.
One example of such an optical projecting apparatus as mentioned above will be explained with reference to FIGS. 22 and 23 which show a scanning exposure apparatus designed to carry out an exposure treatment on a glass substrate. FIG. 22 shows a perspective view schematically illustrating the construction of a conventional scanning exposure apparatus, and FIG. 22 shows a main portion of the scanning exposure apparatus shown in FIG. 22.
Referring to FIGS. 22 and 23, a photosensitive substrate 103 is sustained on a photosensitive substrate stage 102 constituting a bottom portion of a carriage 101 having a U-shaped cross-section, and a mask 105 is retained by a mask stage 104 which is disposed over and facing the photosensitive substrate stage 102.
By way of exposure light irradiated from an optical illuminating system 106, a pattern constituting a portion of region of the mask 105 retained by the mask stage 104 is illuminated, and the exposure light that has passed through the mask 105 is then allowed to pass through an optical image-forming system (or an optical projecting system) 107, thereby enabling the pattern constituting a portion of region of the mask 105 to be transcribed to a portion of the surface region of the photosensitive substrate 103.
In this case, the mask stage 104 bearing the mask 105 and the photosensitive substrate stage 102 sustaining the photosensitive substrate 103 are scanned relative to the optical image-forming system 107, thereby allowing the entire pattern region of the mask 105 to be transcribed to the surface of the photosensitive substrate 103.
The optical image-forming system 107 in this case is constituted by a plurality of optical projecting systems 107a to 107d instead of a single optical projecting system, thereby allowing a plurality of small regions of the mask 105 to be concurrently irradiated by the luminous flux irradiated from the optical illuminating system 106. As a result, the images of these plural number of small regions are concurrently transcribed through a plurality of optical projecting systems 107a to 107d onto the surface of the photosensitive substrate 103.
FIG. 24 shows the exposure images of the scan and step according to the aforementioned scanning exposure apparatus. Referring to FIG. 24, the optical image-forming system (or an optical projecting system) 107 has an exposure field as shown in FIG. 24, so that the optical image-forming system 107 is scanned twice (SCAN 1 and SCAN 2) in the direction A (scanning direction) relative to the photosensitive substrate 103, and, after finishing the scanning of SCAN 2 and being stepped in the direction B, further scanned twice (SCAN 3 and SCAN 4) in the direction C (scanning direction), thus finishing the transcription of the entire mask pattern.
Further, the sustaining mechanism for the photosensitive substrate 103 is provided with an XY stage of long stroke which makes it possible to perform the scan and step. Whereas the retaining mechanism for the mask 105 is provided with an X stage of long stroke for scanning and with a small stroke stage for correcting the Y-direction as well as the rotational direction so as to make it possible to adjust the position thereof relative to the photosensitive substrate 103.
In the exposure operation of the aforementioned exposure apparatus, the projected image of a pattern formed in the mask 105 is required to be accurately superimposed with the pattern layer that has been formed in advance on the photosensitive substrate 103. Therefore, an alignment between the mask 105 and the photosensitive substrate 103 is required to be performed.
For the purpose of performing the alignment, the alignment mark formed on the mask 105 as well as the alignment mark formed on the photosensitive substrate 103 are observed by means of an alignment microscope 108 to detect any misregistration between them, and then, a correction of the positional relationship between the mask 105 and the photosensitive substrate 103 is performed. On both end portions in the direction of Y of both photosensitive substrate 103 and the mask 105, there are a plurality of alignment marks which are formed along the direction of X, so that any one of or plurality of these alignment marks are observed by means of the alignment microscope 108. Then, based on the result detected by this alignment microscope 108, the position and size of the photosensitive substrate 103 relative to the mask 105 are recognized. Therefore, based on this recognition, the position of the mask 105 is adjusted, or the magnification of the optical image-forming system 107 is corrected.
FIG. 25 illustrates the operation of alignment between the mask 105 and the photosensitive substrate 103, which will be performed using the aforementioned scanning exposure apparatus.
For example, when it is found as a result of detection by means of an alignment microscope 108 that the photosensitive substrate 103 is shifted parallel in the directions of X and Y relative to the mask 105 as shown in FIG. 25(a), an actuator which is designed to shift a mask table holding the mask 105 in the direction of X as well as a pair of actuators which are designed to shift a mask table holding the mask 105 in the direction of Y are actuated so as to enable the mask 105 to be shifted parallel to a suitable degree (the correction of shift).
On the other hand, when a rotational mismatch around the Z-axis is found between the photosensitive substrate 103 and the mask 105 as shown in FIG. 25(b), a pair of actuators which are designed to shift a mask table holding the mask 105 in the direction of Y are actuated to a different magnitude from each other to enable the mask 105 to rotate to a suitable degree (the correction of rotation). Furthermore, a difference in relative size is found between the photosensitive substrate 103 and the mask 105 as shown in FIG. 25(c), the magnification of the optical image-forming system 107 is corrected in the direction of Y, and at the same time, the actuator for shifting the mask table in the direction of X is actuated so as to enable the mask 105 to be shifted in the direction of X while allowing the carriage 101 to move for scanning, thereby suitably changing the relative scanning speed between the mask 105 and the photosensitive substrate 103, thus correcting the magnification in the direction of X (the correction of scale).
Specifically, when the photosensitive substrate 103 is extended by a magnitude of 4 ppm in the direction of X, the actuator for shifting the mask table in the direction of X is actuated so as to enable the mask 105 to be shifted by a magnitude of 4 ppm in the direction opposite to the scanning direction of the carriage 101.
By the way, the alignment mark of the mask 105 is formed in advance on the occasion of manufacturing the mask, while the alignment mark of the photosensitive substrate 103 is generally formed on the occasion of the first exposure treatment.
As explained above, since the aforementioned scanning exposure apparatus is provided with an optical alignment system for performing a lap exposure, thus enabling it to perform alignment measurements at a plurality of points on every occasion of scanning, it is possible, on the basis of each result of the alignment measurement, to calculate the linear components of the shift in the scanning direction, of the shift in the non-scanning direction, of the magnification, of the rotation and of the orthogonality, the calculated results being subsequently taken into account in the scanning exposure. With respect to each of the shifts, rotation, orthogonality and the magnification of scanning direction, they can be corrected by shifting the relative position between the mask and the photosensitive substrate. Whereas, with respect to the magnification of non-scanning direction, it can be corrected by correcting the magnification correction mechanism and the shifting mechanism of non-scanning direction, which are disposed in each of the optical image-forming systems.
In the case of the aforementioned conventional exposure apparatus where a plurality of optical projecting systems are employed, a plurality of optical projecting systems (hereinafter, each optical projecting system will be referred to as a module) which are designed to achieve the synthesis of images are individually fabricated at first so as to secure a predetermined performance and subsequently combined with each other at a sufficiently high positional precision for the synthesis of images. Therefore, the dimensional accuracy of each module is required to be strictly controlled for subsequently combining it with one another. Further, there is a problem that the readjustment of positions of these modules after finishing the combination thereof is required to be performed by repeating the step of re-combining these modules from the beginning.
There is also a possibility when the scanning exposure of mask pattern is performed using the conventional exposure apparatus that due to recent trends to further enlarge the size of liquid crystal device and to further enhance the fineness of image, it may be impossible to obtain a liquid crystal device exhibiting a satisfactory performance only through the aforementioned correction of linear components. Namely, in the step of forming a layer in the manufacture of liquid crystal device, the substrate is more likely to be deformed due to the heating thereof in a manufacturing step other than the exposure step. Therefore, while the absolute value of the residual component of error in the linear correction is inevitably increased due to the recent trend to further enlarge the size of substrate as well as device, it is concurrently required to minimize the residual component of error for the purpose of enhancing the fineness of pattern.
For example, the photosensitive substrate to be transferred to a projecting exposure apparatus so as to receive an exposure treatment is generally subjected to plural times of heat treatment during the manufacturing process thereof and also subjected to a repeated light exposure for transcribing the pattern of original image which will be formed over a plurality of layers. Mainly due to the heat treatments in this manufacturing process, the photosensitive substrate is caused to expand or shrink, thus inviting the deformation of the photosensitive substrate. For example, as shown in FIG. 26(a), a photosensitive substrate which is originally rectangular in plan view and rectilinear in each side may be caused to be curved along the direction of Y as shown in FIG. 26(b) or caused to be deformed into a parallelogram as shown in FIG. 26(c) in the course of various processes.
Therefore, when it is tried to perform a light exposure on this photosensitive substrate that has been deformed as shown in FIGS. 26(b) and 26(c), the magnitude of deformation in the direction of Y is caused to change successively as the scanning moved in the direction of X in the light exposure operation, thus raising a problem that it is impossible to sufficiently correct the alignment by way of the aforementioned conventional correction of shift, correction of rotation, and correction of scale. If the exposure of a pattern is performed without undergoing accurate alignment, a lap error that cannot be ignored would be generated between the pattern thus exposed and the underlying pattern, resulting in that the properties of a large number of elements formed on the photosensitive substrate would be varied depending the region of the photosensitive substrate.
The present invention has been made in view of overcoming the aforementioned problem, and therefore, it is an object of the present invention to provide an exposure apparatus which is featured in that the adjustment on the occasion of assembling it can be easily performed, and that even if re-adjustment is necessitated during the operation of the apparatus, the re-adjustment can be finished within a short period of time.
Another object of the present invention is to provide an exposure apparatus which is featured in that the residual component of error involved in the linear correction can be minimized in the scanning exposure of a mask pattern, and that an enhanced fineness can be realized even if the size of the photosensitive substrate as well as the device is increasingly enlarged.
A further object of the present invention is to provide an exposure method which is featured in that the residual component of error involved in the linear correction can be minimized in the scanning exposure of a mask pattern, and that an enhanced fineness can be realized even if the size of the photosensitive substrate as well as the device is increasingly enlarged.
In order to overcome the aforementioned problems, the exposure apparatus according to the present invention is provided with a position detecting means for detecting the position of images projected from a plurality of optical projecting systems, and with means for correcting a position error detected by the position detecting means.
Since the exposure apparatus is provided with the means for detecting the position of projected optical images and with means for correcting a position error detected by the position detecting means, the dimensional accuracy of each module is no more required to be strictly controlled, and even if a readjustment is required after finishing the combination of modules, it is no more required to repeat the combination thereof from the beginning.
The present invention also provides an exposure apparatus for projecting a pattern of mask (mask pattern) onto a substrate through an optical projecting system while synchronously scanning a mask having the pattern and the substrate in a predetermined scanning direction, wherein the optical projecting system is featured in that it is provided with a scanning direction adjusting means which is designed to adjust the position of scanning direction of a projected image to be projected onto the substrate.
The optical projecting system may be constructed such that it is formed of a combination of a couple of Dyson type optical systems each system comprising a reflecting prism, a driving member for driving the reflecting prism, lens and a concave mirror, wherein one of these Dyson type optical systems is provided with an optical magnification adjustment system which is disposed at a midway of optical path formed between the reflecting prism and the lens.
Further, the optical projecting system may be constructed such that is provided with a plurality of optical projecting system modules which are disposed along a direction intersecting the scanning direction, and that the scanning direction adjusting means is designed to adjust the position of a projected image in the scanning direction of these optical projecting system modules.
Alternatively, the optical projecting system may be constructed such that it is provided with a plurality of optical projecting system modules, and that the patterning exposure against the substrate is performed by allowing a portion of images projected by these optical projecting system modules to be overlapped with each other.
Additionally, the scanning direction adjusting means may be designed so as to adjust the position of projected image in accordance with changes in configuration of the substrate. Further, the scanning direction adjusting means may be provided with a magnification adjustment mechanism for performing the adjustment of magnification of the optical projecting system and/or an image rotation mechanism for rotating a projected image produced through the optical projecting system.
The present invention also provides an exposure method for projecting a pattern of mask (mask pattern) onto a substrate through an optical projecting system while synchronously scanning a mask having the pattern and the substrate in a predetermine scanning direction, wherein the exposure method is featured in that it comprises a step of adjusting the position of scanning direction of a projected image to be projected on the substrate by means the optical projecting system.
In this case, the optical projecting system may be constructed such that it is provided with a plurality of optical projecting system modules which are disposed along a direction intersecting the scanning direction, and that the adjustment of position of scanning direction is performed by adjusting the position of a projected image in the scanning direction of each of these optical projecting system modules.
Alternatively, the optical projecting system may be constructed such that it is provided with a plurality of optical projecting system modules, and that the patterning exposure against the substrate is performed by allowing a portion of images projected by these optical projecting system modules to be overlapped with each other.
Additionally, the adjustment in position of scanning direction may be performed in accordance with changes in configuration of the substrate.
Further, the exposure method according to the present invention may further comprises a step of performing the adjustment of magnification of the optical projecting system and/or a step of rotating an image projected through the optical projecting system.
The adjustment in position of a projected image during an exposure step by means of the optical projecting system can be performed in accordance with changes in configuration of the substrate which may be generated in the course of treating steps. As for the magnitude in deformation of substrate, it can be determined by measuring a plurality of alignment marks disposed at predetermined locations of the substrate. Further, it is also possible to accurately measure any deformation all over the substrate by measuring the position of patterns which are regularly arranged on the surface of the substrate. It is possible in this case to approximately accurately grasp the magnitude of deformation of substrate by measuring at first the position of patterns which has been detected through a pattern matching and then, by statistically processing the date obtained from the aforementioned measurement.
It is now possible to adjust the relative positional relationship between an image projected and the substrate by rotating or shifting the image projected by the optical projection system, or by changing the magnification of image thus projected so as to conform it with the deformation of substrate which has been measured as mentioned above.